This exploratory study aimed to determine the relationship between perceived teacher self-disclosure, writing performance, and gender of Malaysian English as a Second Language (ESL) undergraduates. A self-administered questionnaire was distributed to 75 students who had enrolled in a university writing course at the end of their terms. Fifty-seven students had responded. The Perceived Teachers' Self-Disclosure Scale, which indexes three aspects of teacher self-disclosure namely amount, relevance, and negativity was used to determine the undergraduates' perceptions of their perceived teachers' self-disclosure. Scores for writing performance were gathered from the results obtained by the students in their final examination for the writing course. The relationship between perceived teacher self-disclosure and writing performance was analyzed using the Pearson Product-moment Correlations test. The difference between perceived teacher self-disclosure and gender was analyzed using the independent sample t-test. The results showed a small, positive correlation between two aspects of teacher self-disclosure (amount and relevance) and writing performance. The results from this study demonstrated that ESL students perceived that relevant teacher self-disclosure, relating to course content, had important implications for their writing performance. Thus, teacher self-disclosure is an important element of classroom instruction that could be used to enhance content knowledge, especially in idea generating, self-voice and opinion among ESL students in a writing class. The results also showed a significant difference in one dimension of teacher self-disclosure, negativity, and gender. Further comprehensive studies should be conducted to gauge the implications of perceived teachers' self-disclosure to the teaching and learning aspects in ESL writing classrooms.